1. Field of the Invention
The present invention relates generally to an insulating building material and method of manufacture of the same and the use of the same in construction; more specifically, to a cellulosic cementitious material providing both compressive strength and insulation and a method for mixing the cellulose and cementitious materials to form a paste which upon curing is both compressively strong and highly insulating.
2. Related Art
The building trades have long sought a building material that combined compressive strength with high insulating qualities. Various concrete mixtures have been made with various porous aggregates and by incorporation of a cement paste into a cellular matrix of air voids to create an insulating concrete, but these have suffered from having a 28-day compressive strength from only 100 to 1000 psi (0.69 to 6.9 MPa). The environmental movement has increased the demand for reuse of the substantial amount of paper generated each year. Paper recycling bins positioned in school and church parking lots to encourage the reuse of scrap paper is a testament to the public demand for ecologically sensitive paper recycling.
The use of a combination of recycled paper and Portland cement, called papercrete, has increased public attention and lead to substantial experimentation of this form of building material. For example, U.S. Pat. No. 5,350,451 to Patterson teaches mixing water and paper products in a high speed shearing blender to form a comminuted slurry then mixing in cement in a ratio of four to one. Patterson comminutes the paper feedstock by running through a cutter running at around 3000 rpm or higher. This wet comminuted paper is then coated with the cement and the mixture is dumped on a screen to allow water to drain off. Patterson suggests, when making blocks from the slurry, to allow the water to drain off for sixty to ninety minutes and the concrete to begin to set before placing the mixture in the molds. Not only is the output from this process limited, the time to mix economically useable building products is generally too slow for commercial use.
Other patents discuss the use of cellulose to reinforce concrete mixes; see, for example, U.S. Pat. No. 6,942,726 to Cook et al. Various methods have been offered for dispersing cellulose fibers in water for use. See for example U.S. Pat. No. 5,849,155 to Gasland. Other patents have suggested the addition of insulation materials to cement blends to form highly insulating cementitious matrices and have provided teaching as to the method of manufacture of these products. See U.S. Pat. No. 5,641,584 to Andersen et al.